Transport and elastic scattering times as probes of the nature of impurity scattering in single and bilayer graphene

TL;DR

This study measures transport and elastic scattering times in monolayer and bilayer graphene to understand impurity scattering mechanisms, revealing similar ratios but different dependencies, suggesting short-range resonant scatterers like vacancies dominate.

Contribution

It provides experimental determination of scattering times in graphene and compares them with theoretical models to identify the dominant impurity scattering mechanism.

Findings

The ratio τ_tr/τ_e is approximately 1.5 in both graphene systems.

Transport and elastic scattering times depend differently on carrier density.

Short-range resonant scatterers, such as vacancies, are likely the main impurities.

Abstract

Both transport $\tau_{tr}$ and elastic scattering times $\tau_{e}$ are experimentally determined from the carrier density dependence of the magnetoconductance of monolayer and bilayer graphene. Both times and their dependences in carrier density are found to be very different in the monolayer and the bilayer. However their ratio $\tau_{tr}/\tau_{e} $is found to be of the order of $1.5 $ in both systems and independent of the carrier density. These measurements give insight on the nature (neutral or charged) and spatial extent of the scattering centers. Comparison with theoretical predictions yields that the main scattering mechanism in our graphene samples could be due to strong scatterers of short range, inducing resonant scattering, a likely candidate being vacancies.